1. Field of the Invention
The present invention relates to a brake fluid pressure controller for vehicles that have a brake anti-locking control means.
2. Description of the Prior Art
It is known that a brake fluid pressure control valve, which is called a proportioning valve and decreases the pressure of incoming brake fluid entering the valve at a prescribed rate in order to increase the pressure applied to the brake fluid leaving the valve, is provided in the rear wheel liquid fluid pressure line system of a vehicle in order to approximate the distribution of the front and rear braking force of the vehicle to an ideal one, as disclosed in the U.S. Pat. No. 3,479,095.
Such a proportioning valve is also provided in a vehicle having a brake anti-locking controller, as disclosed in the U.S. Pat. No. 4,652,060. The valve functions so that the braking force applied to the front wheels of the vehicle and that applied to the rear wheels thereof are of equal magnitude, as the braking force in the front and the rear wheels is less than a prescribed magnitude at the initiation of braking of the vehicle. It also functions in such a manner that the braking force applied to the rear wheels is made lower in magnitude than that applied to the front wheels, as the respective magnitudes of braking force are equal to or higher than the prescribed magnitude after the initial stage of the braking, thus approximating and comparing the times for locking the front wheels as well as locking the rear wheels with each other in order to prevent the loss of initial braking force and premature anti-locking control of the rear wheels.
Another such proportioning valve has an inertia member fitted with an inertial valve action element for cutting off the transmission of brake fluid when a prescribed rate of deceleration is applied to the member, as disclosed in the U.S. Pat. No. 4,116,493. As for a vehicle such as a truck, which differs much in ideal distribution of braking force between the loaded and unloaded states of the vehicle, the pressure of brake fluid, which is decreased by yet another proportioning valve, is altered depending on the load in the vehicle in such a manner that the pressure of the brake fluid, which initiates and controls the braking force for the rear wheels of the vehicle, is increased in accordance to an increase in the load on the vehicle, thus providing the valve with a braking force distributing property responsive to the load as shown in FIG. 6 of U.S. Pat. No. 4,116,493.